15 is the center number............from 10 - 20...........................matching double digits to double digits..............1 to 2...........like 1/2..........the c line..............14.13 i.............is between 14i and 15i..................................3 fives in the square root of 13...........which starts out.......3.60555.............3 fives..............5 + 5 + 5 = 15..............................

The triangle...............is the square root of 3 equil triangle............the only kind that can be inscribed in the unit circle................the square...................very crude one...........is the square root of 2 square..........the only kind of square..........that can be inscribed in the unit circle.................they overlap at the top......................(0, 1)..............................on the Y axis.............1 up..........0 and 1.............1/2 is right between them.................................a square has 360 degrees..........the same as a circle.............................................an equil triangle has 3 60 degree angles.....................see a pattern?.....................................so the other two angles are 15 and 15...............between the square root of 3 triangle and the square root of 2 square.................b/c they are symmetrical...............and the difference between 90 and 60 is 30.........half of 30 is 15.................................15 is dead center from 10 to 20.............................on either side...........is 11 and 13..............and 17 and 19...........11 + 13 = 24.....................................17 + 19 = 36...................36............like full circle...............11 + 13 + 17 + 19 = 60.............1/6th full circle and like a truncated full circle..................